Tetrafluoroethylene polymer aqueous dispersions have been used to coat substrates such as fabrics to provide a protective coating. Frequently, such dispersions contain filler materials to enhance the covering power (i.e., to aid in providing a continuous protective coating free of pinholes and the like. In the past a number of patents have dealt with the problem of maintaining the filler in dispersed form during periods of storage of the dispersions before use as coatings. Thus, Fay, U.S. Pat. No. 2,717,220, employs a nonionic surfactant in order to maintain filler (cryolite) in suspension in polytetrafluoroethylene dispersions. Ribbons, U.S. Pat. No. 3,830,770, employs certain water soluble electrolytes, e.g. Ba(NO.sub.3).sub.2, having ionic strengths of between 0.01 and 0.3 moles per kg to aid in maintaining glass beads in suspension. Richter, U.S. Pat. No. 4,169,087, describes that selected sodium phosphates will increase the viscosity of tetrafluoroethylene aqueous dispersion. Olsen, U.S. Pat. No. 4,391,930 teaches that good shelf life can be obtained in certain tetrafluoroethylene aqueous dispersions by using certain glass bubbles as the filler.
It would be desirable to enhance the flowability of tetrafluoroethylene aqueous dispersions onto fabric substrates and to improve the coverage uniformity of the dispersion on the substrate to such an extent that presence of filler particles is no longer needed.